As much as it broke Welsh hearts, by the letter of the law, the tackle was illegal; Warburton took the player beyond horizontal and dropped him to the turf. However, I don't believe it was dangerous at all. What should happen now is a review of the law. Correct efforts were made to protect players from spear tackling but the rulings have gone too far and we're now in danger of losing the element of competition in the tackle.
Red cards should be reserved for acts of malice outside the rules, not thumping hits.
At least the Welsh can hold their heads high in the knowledge that they fought for 80 minutes with 14 men, as opposed to England, who limply strung together the occasional fluent passage while being outclassed by an undercooked French team.